Validate an email address using RegularExpressionValidator in asp.net c#

RegularExpressionValidator - Validate email address

RegularExpressionValidator control determine whether an input control's entered value matches
a pattern defined by a regular expression. this validation control is very useful to check
predictable sequences of characters. regularexpressionvalidator is mostly use for validate
email address, social security number, telephone number, postal (zip) code etc. you also need to
add a requiredfieldvalidator control because regularexpressionvalidator cannot validate empty value
control. visual studio and visual web developer .net IDE can auto generate regularexpressionvalidator
validation expression. it is a very useful and time saving feature of visual studio. when validation failed
regularexpressionvalidator control show a predefined error message.

this example demonstrate how can we validate user inputted email address by regularexpressionvalidator.
when user input email address and press the submit button, the regularexpressionvalidator control's
validation expression check that the inputted email is a well formed email address or not. if it is not
a valid formatted email address then validation failed and stop form submission.